A Compact SPAD Pixel With Active Quenching And Recharging

This paper introduces a compact single photon avalanche diode (SPAD) pixel for high-density 2D array imagers. A novel active quench/reset circuit is proposed to significantly improve the reliability of avalanche quenching and recharging. Meanwhile, a simple analog counter with charge sharing principle is applied to effectively lower pixel area. Designed by standard 0.18 μm CMOS technology, the SPAD pixel with a pitch of 34 μm features a high fill factor as much as 19%. The post-layout simulation shows the dead time of the quench/reset circuit is only 5 ns, indicating the detectable photon rate is up to 200 Mbit/s. In addition, the low differential nonlinearity (DNL) within 1LSB and the extremely low no uniformity of less than 0.2% is obtained for the analog counter.